Remove optional extra value from credentials JSON

Secrets manager entry holding DB credentials could have
dbInstanceIdentifier or dbCluesterIdentifier depending on the type of
database in use. This change removes both keys.

Also checks if key is present in dict before attempting to delete it.

src/config.py

@@ -390,8 +390,9 @@ def get_db_connection_params() -> dict:
         connection_params = json.loads(db_credentials)
 
         connection_params["user"] = connection_params["username"]
-        for k in ("dbinstanceidentifier", "engine", "username"):
-            connection_params.pop(k, None)
+        for k in ("dbinstanceidentifier", "dbClusterIdentifier", "engine", "username"):
+            if k in connection_params:
+                connection_params.pop(k, None)
 
     if None in connection_params.values():
         raise ValueError(